Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 28-04-2013, 03:06   #16
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,758
Re: Mast spreaders, are they under lots of pressure ?

Quote:
Originally Posted by Andrew Troup View Post
Excellent advice. One other point to keep the mast from inverting, which is often overlooked (it's a counsel of perfection, but worth thinking about when new sails are ordered)

Ideally the head of the sail in the deep reefed positions should fall at, or preferably a little above, the nearest attachment point of an inner forestay or babystay.
Are you sure that makes any difference? As far as I know, the load is not concentrated at the head of the sail -- it's spread across the luff. That's because unlike the case with a headsail, the main is not attached to a stay.

I am pretty sure it doesn't really make any difference; nevertheless, my deeply reefed position is with the top of the leech (it's not exactly the head, because I have in-mast furling) positioned opposite the point at which the inner forestay is attached to the mast. So the main is symmetrical with the staysail. I've always thought that this habit was just a bit of superstition on my part.
__________________

__________________
Dockhead is offline   Reply With Quote
Old 28-04-2013, 04:23   #17
Registered User
 
Snowpetrel's Avatar

Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,071
If you've got an inner forestay, and a reasonable section mast I don't think it's an issue.
__________________

__________________
My Ramblings
Snowpetrel is offline   Reply With Quote
Old 28-04-2013, 04:23   #18
Registered User

Join Date: Feb 2012
Posts: 2,441
Re: Mast spreaders, are they under lots of pressure ?

Quote:
Originally Posted by Dockhead View Post
Are you sure that makes any difference? As far as I know, the load is not concentrated at the head of the sail -- it's spread across the luff. ....
Leech tensions are high on tall mainsails, and they appear at the masthead in the form of halyard tension pulling downwards, and a significant aftwards force from the horizontal component of the leech vector.

That aftwards force is responsible for the automatic depowering that you get in fractional rigs, as the increasing leech tension in puffs causes the topmast to curve aft.

And in masthead rigs, the nett longitudinal force at the masthead from the vector sum of the loads in the headsail luff, the forestay and backstay, and the leech load from the main, (the considerable leech load from the genoa or blade jib is virtually vertical so it doesn't really come into the picture) is as much as three quarters of the lateral load at the masthead.

It's directed aft.

If the backstay adjuster is released (or the stay fails !), as long as you're hard on the wind and the main remains sheeted hard with plenty of breeze, the forestay tension will not be lost, and in the case of an in-line rig, that's purely from the leech load on the mainsail.
__________________
Andrew Troup is offline   Reply With Quote
Old 28-04-2013, 23:21   #19
Senior Cruiser

Cruisers Forum Supporter

Join Date: Nov 2005
Location: Tasmania
Boat: VandeStadt IOR 40' - Insatiable
Posts: 2,317
Images: 91
Re: Mast spreaders, are they under lots of pressure ?

If you use non-aluminium rivets (i.e. Monel, stainless, etc) into aluminium mast, make sure you use an appropriate anti-corrosion compound. I use Duralac, but there are others available too.
__________________

__________________
Weyalan is offline   Reply With Quote
Reply

Tags
mast

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 00:29.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.